The present invention relates to temperature control systems and, in particular, to a temperature control system for a liquid chromatography system.
A basic module of a liquid chromatography system is the chromatographic column, sometimes referred to as an HPLC column, through which the sample/solvent flows prior to being detected. Such columns typically comprise a hollow tube that is filled with an appropriate non-reactive adsorbent, such as particles of silica gel, alumina and polyamide, among others. During use and upon injecting a desired volume of a sample into an appropriate solvent, the mixture is forced under pressure through the chromatographic column, where the various compounds of the sample are separated at a rate dependent upon the type of compound, prior to the compounds being sequentially detected by the detector element.
As has long been known, the rate of separation of the compounds is positively affected by the application of heat to the liquid column. Furthermore, by controlling the temperature of the column, the peak retention time reproducibility from sample to sample is dramatically affected, while maintaining a relatively constant base-line or background electrical noise level due to solvent flow in the detector.
Heretofore, temperature controllers employed in conjunction with liquid chromatography systems have been of a water bath, air bath or high mass (e.g. aluminum block) type. The temperature of the surrounding air, water or block in contact with the liquid column is then controlled so as to produce a stable and reproducible temperature gradient over the exterior surface of the chromatographic column. Such temperature controllers, however, suffer from a number of problems, not the least of which are large bulk, high cost, long cooling times, awkward apparatus set-ups and excessively long input and output tubing runs to and from the column.
The present invention, however, presents a low cost alternative temperature control system that essentially does away with all of the above referenced problems. Furthermore, the present invention permits the tailoring of the temperature gradient over the chromatographic column so as to produce either a uniform gradient or a profiled gradient (i.e. uniformly heated solvent/sample) from end-to-end of the column. These objects and advantages are achieved via the use of a temperature controlled thin film heater/sensor that is containably mounted around the column via a spiral retainer and in some instances around a pre-heater and/or post-heater. A temperature controller senses the column surface temperature via a thin film sensor element and appropriately switches power to a thin film heater element so as to maintain the temperature of the column at a uniform, operator selected temperature. Similarly, the pre and post-column heaters are wrapped with appropriate thin film heater/sensors so as to appropriately control the temperature of the liquid flow before and/or after entering and leaving the column. The specific apparatus and its operation, and the above objects and advantages, as well as others, will, however, become more apparent upon a reading of the following description with respect to the following drawings.